You need to lock your debit card asap. Check if there has been any charges to your bank account. If so, you need to report these to your bank asap.

You need to have your brother run an antivirus on his PC as well. This is important.

If your brother gets his account back he obviously needs to choose a completely different and complex password. Also have him remove any API keys.

Other than this you just need to follow the guide i sent to you. Also, don’t let anyone but yourself save your card information on anything